diff --git a/instruments/readers/nasa_ames_reader.py b/instruments/readers/nasa_ames_reader.py
index 1601542..4731be7 100644
--- a/instruments/readers/nasa_ames_reader.py
+++ b/instruments/readers/nasa_ames_reader.py
@@ -152,10 +152,22 @@ def read_nasa_ames_as_dict(filename, instruments_dir: str = None, work_with_copy
                          sep="\s+",
                         header=header_length - 1, 
                         skip_blank_lines=True)
+        
+        df['start_time'] = df['start_time'].astype(str).str.strip()
+        df['end_time'] = df['end_time'].astype(str).str.strip()
+
+        df['start_time'] = pd.to_numeric(df['start_time'], errors='coerce')
+        df['end_time'] = pd.to_numeric(df['end_time'], errors='coerce')
+
         # Compute actual datetime from start_time and (if present) end_time
-        df['start_time'] = df['start_time'].apply(lambda x: start_date + timedelta(days=x))
+        df['start_time'] = df['start_time'].apply(
+            lambda x: start_date + timedelta(days=x) if pd.notna(x) else pd.NaT
+        )
+
         if 'end_time' in df.columns:
-            df['end_time'] = df['end_time'].apply(lambda x: start_date + timedelta(days=x))
+            df['end_time'] = df['end_time'].apply(
+                lambda x: start_date + timedelta(days=x) if pd.notna(x) else pd.NaT
+        )
 
         # Create header metadata dictionary
         header_metadata_dict = {